PROJECT SUMMARY Despite extensive anti-drinking efforts, 8.5% of US adults abuse or are dependent on alcohol. Excessive drinkers are at higher risk for morbidity and negative health consequences such as such as cancer and neurocognitive decline. While genetic sequence variation contributes to alcohol addiction, mounting evidence suggests that DNA methylation may provide complementary information. First, methylation marks may improve the prediction of alcohol addiction risk as they can capture fundamentally different disease processes and directly affect gene expression. Second, methylation studies may increase our understanding of alcohol addiction. For example, phenomena such as withdrawal and tolerance suggest that repeated alcohol use creates a ?biological memory? affecting future responses to alcohol. Because alcohol induced epigenetic changes can persist over time and have lasting effects, DNA methylation could shed light on such mechanisms. Third, in addition to tissue specificity, substantial concordance in methylation also often exists across tissues, including brain and blood. The possibility that methylation sites in brain can have corresponding marks in blood that can be measured cost-effectively in easy to collect genomic DNA from blood, makes these sites potentially very powerful biomarkers for use in the clinic to improve the trajectory of alcohol addiction development, diagnosis, and treatment. PAR-16-234 calls for innovative analyses of existing data to study alcohol addiction. To identify methylation biomarkers predicting alcohol use and related health risks, we will bring together an unprecedented combination of existing next-generation sequencing data to perform methylome-wide association studies (MWAS) in three samples with PhenX measures of alcohol. Furthermore, whereas alcohol methylation studies have historically been restricted to a limited number of CpGs, we propose to screen all ~28 million common CpGs in the human genome. The sample size, ~3,300, which will be the largest alcohol methylation study to date, is unprecedented, offering the opportunity to perform methylation biomarker investigations with high statistical power at low cost because the methylation data has already been generated. Successful completion of this project will generate biomarkers to improve the diagnosis and prognosis of alcohol addiction and related health risks.